AREF1

where name is a symbol, alist is a 1-dimensional array and index
is a legal index into alist. This function returns the value
associated with index in alist, or else the default value of the
array. See arrays for details.

This function executes in virtually constant time if alist is in
fact the ``semantic value'' associated with name (see arrays).
When it is not, aref1 must do a linear search through alist. In
that case the correct answer is returned but a slow array comment is
printed to the comment window. See slow-array-warning.